1. Field of the Invention
The present invention relates to a liquid ejection head and an image forming apparatus, and more particularly, to a liquid ejection head and an image forming apparatus comprising a plurality of nozzles from which liquid is ejected, wherein the direction of ejection of the liquid ejected from the plurality of nozzles can be deflected.
2. Description of the Related Art
Recently, image forming apparatuses provided with a liquid ejection head formed with a plurality of nozzles from which ink is ejected have become widespread, an image being formed on the recording medium by ejecting ink from the plurality of nozzles of the liquid ejection head toward the recording medium while the liquid ejection head and the recording medium are moved relatively with respect to each other.
Furthermore, it is also known that the direction of ejection of the ink can be deflected by means of actuators of various types provided for each nozzle.
Japanese Patent Application Publication No. 56-133173 (in particular, FIG. 2) and Japanese Patent Application Publication No. 57-152958 (in particular, FIGS. 1 and 2) disclose technology in which a piezoelectric element is affixed to the outer wall surface (outer circumference) of a cylindrical nozzle tube, and the direction of ejection of liquid is deflected by directly deforming the wall surface of the cylindrical nozzle tube by driving this piezoelectric element.
Japanese Patent Application Publication No. 58-500515 (in particular, FIGS. 3 and 4) discloses technology in which an electromagnet is provided adjacently to the side of a nozzle formed in a nozzle plate, and the direction of ejection of the liquid is deflected by causing the nozzle plate to tilt by means of this electromagnet.
Japanese Patent Application Publication No. 7-276634 (in particular, FIGS. 1, 3 and 5) discloses technology in which a piezoelectric element which distorts in an oblique shape with respect to the direction of voltage application (a so-called “shear mode” element) is formed on the inner wall of the restrictor section (orifice section) forming a nozzle in a nozzle plate, and the direction of ejection of liquid is deflected by directly deforming the wall surface of the restrictor section forming the nozzle, by driving this piezoelectric element.
Moreover, Japanese Patent Application Publication No. 7-276633 (in particular FIGS. 1, 3 and 5) discloses technology in which a swayable deflection plate is provided on the inner wall of a restrictor section (orifice section) formed as a nozzle in a nozzle plate, and the direction of ejection of liquid is deflected by directly deforming the wall surface of the restrictor section forming the nozzle, by causing the deflection plate to sway by means of a coil provided adjacently to the side of the deflection plate.
In recent years, there have been demands for improved image quality and higher recording speeds in image forming apparatuses having liquid ejection heads, and in order to achieve these demands, it is essential to increase the number of nozzles and to arrange these nozzles at higher density. In order to seek to increase the number of nozzles and to raise the density of the nozzle arrangement in this way, it is difficult to achieve high density unless the electrical wires peripheral to the nozzles are also arranged at increased density.
However, if an actuator forming a deflection device (for example, a piezoelectric element or electromagnet) is individually provided for each nozzle in order to deflect the direction of ejection of the liquid, as described in the related art patent references described above, then it is necessary to provide spare surface area to install the actuators, in addition to the surface area for installation of the nozzles, or the length of the nozzles is required to be increased. Furthermore, since electrical wires for driving are provided for actuators respectively, in other words, since an electrical wire is required for each nozzle, then even if the nozzle diameter is reduced, for example, it is difficult actually to achieve high density of a large number of nozzles.
For example, the technology described in Japanese Patent Application Publication No. 7-276634 requires the formation of a piezoelectric element on the inner wall of each of the nozzles, and the installation of an electrical wire to each of the piezoelectric elements on the inner walls of the nozzles. Alternatively, a coil is provided in the vicinity of each of the nozzles, and electrical wires are required to be installed so as to lead to the coils in the vicinity of the nozzles respectively. The installation of actuators and electrical wires in this fashion is not necessarily difficult in the case of a small number of nozzles (for example, 16 nozzles); however, when a lot of nozzles are used, it becomes difficult in practical terms to arrange the nozzles at high density because it is necessary to install actuators and electrical wires for the nozzles respectively.
Japanese Patent Application Publication No. 56-133173, Japanese Patent Application Publication No. 58-500515 and Japanese Patent Application Publication No. 57-152958 do not mention technology suitable for high-density arrangement of a large number of nozzles.
More specifically, the commonly known related art technology can be applied in limited conditions, where the nozzles are not arranged at high density, or where the number of nozzles is small; however, it is difficult to manufacture a device using normal manufacturing equipment under conditions where the high density is required.